Data storage systems commonly employ replication solutions for protecting the data they store. Conventional replication solutions furnish either block-based solutions, e.g., for replicating LUNs (Logical Unit Numbers—although the term generally refers to the units themselves) or file-based solutions, e.g., for replicating file systems or individual files. Block-based solutions operate on storage volumes, e.g., using Fibre Channel or iSCSI (Internet Small Computer System Interface) protocols, whereas file-based solutions operate on files and file systems, e.g., using NFS (Network File System), CIFS (Common Internet File System), or SMB 3.0 (Server Message Block) protocols.
A well-known example of a block-based replication solution is the RecoverPoint system available from EMC Corporation of Hopkinton, Mass. RecoverPoint systems include a replication splitter realized in software, e.g., on a storage processor (SP) that accesses a local block-based array, one or more local replication appliances, and one or more remote replication appliances connected to a remote array configured as a replica site. As a data storage system receives IO requests specifying data to be written to a particular LUN on the local block-based array, the replication splitter intercepts the IO request and sends it to the local replication appliance (or appliances), e.g., over a Fibre Channel or iSCSI connection. The local appliance communicates with the remote appliance, e.g., over a WAN (Wide Area Network), and manages the storage of the data specified in the IO request at the replica site. In this manner, the replica site is made to store data that provide a redundant copy of data on the LUN, which may be used to recover the contents of the LUN in the event of a failure on the local array.
A well-known example of a file-based replication solution is the Celerra Replicator™ V2, also available from EMC Corporation of Hopkinton, Mass. Replicator V2 includes software for performing replication on files and file systems. Replicator V2 operates by taking snaps (e.g., point in time copies, also known as “snapshots” or “checkpoints”) of files and file systems at a local site, comparing current snaps with previous snaps, identifying differences, and sending the differences to a destination site. The destination site accumulates and stores the differences, which can be reconstituted to recover the file or file system being replicated in the event of a failure at the local site. File-based replication solutions often provide advanced features for establishing and maintaining replication sessions, managing recovery and failover, and ensuring that particular settings and restrictions applied to file systems being replicated carry over to replicas at the destination site.
Conventional replication solutions may perform synchronous replication or asynchronous replication. “Synchronous” replication refers to replication that takes place in band with IO requests as the IO requests arrive. With synchronous replication, data conveyed in individual IO requests are generally persisted to a replica site on an individual basis, e.g., one-by-one, as the IO requests are processed. In contrast, “asynchronous” replication is performed out of band with individual IO requests, with replicas generated, for example, on demand, at regular intervals, and/or in response to particular events. Bearing this distinction in mind, RecoverPoint may be regarded as a synchronous replication solution, although it may also provide asynchronous capabilities. Replicator V2 may be regarded as an asynchronous solution, as acquiring snaps and computing differences between them are performed out of band with IO processing.